Bioluminescent sensor system

ABSTRACT

In a bioluminescent sensor system there is provided a fluid path for passing vapors across a bioluminescent microorganism sensor to momentarily test for a specific vapor and a recirculating fluid path for otherwise passing humidified air across the sensor to provide humidification to condition the sensor environment to preclude the loss of moisture from the sensor microorganism and stabilize the luminescence and response characteristics of the sensor culture.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a bioluminescent sensor system and inparticular to a detection system including at least one sensor foridentifying specific vapors, with fluid paths for alternatelyintroducing fluid sample for testing, and humidified fluid forconditioning the sensor and its environment.

2. Description of the Prior Art

In fluid or air sampling systems in use with bioluminescent sensorswhere the sensor is typically isolated, except during short sampling orhumidifying intervals, such as disclosed in U.S. Pat. No. 3,370,175entitled Toxicant Detector for inventors A. L. Jordan et al, issued onFeb. 20, 1968 and assigned to the owner of the present invention,sensitivity of the detection medium may be affected. This can be causedby a loss in moisture from the agar medium or other suitable substrate,on which the detection medium, including the luminous culture comprisingmicroorganisms such as bacteria or fungi, are grown. Air samplingsystems which provide only for sample fluid or air continuously blowingacross the sensors, if not otherwise compensated for, can be the causeof unsatisfactory results since the sensor loses moisture and canrespond to humidity changes, and the total luminescence and reactivityof the culture may be changed and generally decreased. Air samplingsystems, where the bioluminescent sensor is constantly exposed to theatmosphere being tested, cause the sensor to become equilibrated to thespecific gas under test and the biosensor will not respond to that gasunless it is above the ambient concentration.

Typical solutions to these humidification problems involve so-calledstop-flow methods where the air flows across a sensor and is turned onand off at a rate dependent upon the frequency of sampling and in-linehumidification where the sample passes through a humidifier. However,the first solution has drawbacks in that the bioluminescent sensordetector also responds to changes in humidity and air flow therebydisturbing it and causing it to react to disturbances other than that ofthe specific gas under investigation. Drawbacks with respect to thelatter configuration are the loss of sample in the humidifier and thedecrease of response to a specific vapor if low levels are alreadypresent in the environment.

These sensor microorganisms when cultured are grown under conditions ofsubstantially 100% humidity. Therefore, sensor viability and sensitivityis maximum at high humidities. In addition, when subjected to varyinghumidity and fluid flow conditions, its response is affected.

SUMMARY OF THE INVENTION

An inventive system and method to solve these problems regarding changesin detectability of the microorganism sensors due to moisture contentchanges is hereby provided. The invention contemplates fluid conduitsystems having operational valves, or switching apparatus includingfluids or hydraulic control systems whereby a continual flow ofhumidified clean air passes across the surface of the bioluminescentsensor during a standby or non-test period which continual flow can bebriefly interrupted during the test period to allow fluid atmosphereunder test to flow and pass over the microorganism sensor to determinethe presence of a specific vapor.

This type of pulse-sampling method provides for a very shorttime-duration pulse of test air to be presented to the sensor which willpreclude any appreciable change to the bioluminescent characteristics ofthe detector, unless of course the specific vapor under sample isdetected. During the short pulse, the moisture change or loss to thesensor is insignificant and will not affect resolution of the testresults.

In application an embodiment according to the principles of thisinvention is suitable for use in either a single sensor system or asystem where more than one sensor is contemplated, such as disclosed inU.S. Pat. No. 3,849,653 issued Nov. 19, 1974 entitled MultichannelBioluminescent Sensors assigned to the assignee of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a fluid sampling system accordingto the principles of the present invention, illustrating a recirculativehumidification mode;

FIG. 2 is an illustration of a portion of the fluid sampling system ofFIG. 1, illustrating a fluid sampling mode;

FIG. 3 is an alternate embodiment of a fluid sampling system accordingto the principles of the present invention, illustrating a recirculativehumidification mode; and

FIG. 4 is an illustration of a portion of the fluid sampling system ofFIG. 3, illustrating a fluid sampling mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the interest of providing an improved bioluminescent sensor samplingsystem including elements for providing for the stabilization of theluminescence of the sensor culture, there is shown in FIGS. 1 and 2,schematic illustrations of one preferred embodiment of such a system andin FIGS. 3 and 4 illustrations of another. Frequently, it is desirableto have the actual elements of such an embodiment portable for easymaintainence and handling. Portability is particularly desirable for lawenforcement and safety enforcement applications where the vapor underinvestigation is at variable locations. In FIG. 1, for example, a sensorassembly 10 and a humidifier 12 are schematically illustrated as beingencased within a remote sensor assembly unit 14. Sensor assembly unit14, for example, can be a hand-held unit and can be easily manipulatedand of convenient size to probe and sample atmospheres in confinedenvironments. A base assembly unit 16, which can be remotely disposedfrom the sensor assembly unit 14, includes a pump 18 for recirculatingfluid across a bioluminescent sensor element comprising a microorganismin the sensor assembly 10. The base unit 16 also includes a suitablevalve 20 which, for example, may be controlled by an actuating device 22to assume either a first position, as illustrated in FIG. 1, for arecirculating mode to pass clean humidified air over the sensor cultureor a second position, as illustrated in FIG. 2, for a sampling mode totest fluid sample from the atmosphere.

Pump 18 provides for a pressure differential to draw a fluid sample fromthe atmosphere through an input conduit or inlet port 24 which is indirect fluid communication with the sensor assembly 10 and the sensorculture. A fluid conduit 26 extends between the sensor assembly 10 andthe pump 18. Conduit 26 constitutes the outlet port of the sensorassembly 10. The pump 18 is in fluid communication with the valve 20through a conduit 28 defining a portion of the recirculating path whichfurther extends through the valve 20 to and through a conduit 30communicating with the humidifier 12 through filter 31. The humidifier12 and the filter 31 clean, scrub and humidify the recirculating fluidwhich passes through a conduit 32, defining the remaining portion of therecirculating path, to directly communicate with the culture of thesensor assembly 10.

In this preferred embodiment, remote sensor assembly unit 14 may beoperably disposed an appreciable distance from the base assembly unit 16in which case it may be desirable to have, either part or all of theconduit 26 which extends between the sensor 10 and the pump 18 and theconduit 30 which extends between the humidifier 12 and the valve 20, offlexible or other suitable construction to accommodate both the possiblemanipulation of the remote sensor assembly unit 14 and its remotedisposition from the base assembly unit 16.

As hereinbefore mentioned, FIG. 1 illustrates the recirculating mode ofthe sensor sampling system, where the cleansed and moisturized fluidpasses through the valve 20 in a closed recirculating channel 34internal to the valve 20. When sample selecting or testing is conducted,a separate control unit 35 provides power and signal control to anactuating assembly 22 to cause it to move the valve 20 to a position, asillustrated in FIG. 2, aligning channel 36, internal to the valve 20,with the conduit 28 passing between the pump 18 and the valve 20. Thisestablished path thereby allows some fluid to pass through an outputconduit 38 to the atmosphere. The motion and resultant position of thevalve 20 also closes the recirculating path back to the humidifier 12and the sensor 10. In that the pump 18 still provides a pressure drop,atmosphere is caused to move through the sample intake tube 24 and henceto be drawn across the biosensor in sensor unit 10. The sample draw tothe biosensor is caused by the action of the valve 20.

The sampling period is preferably of very short duration and usuallyless than 5 seconds although longer periods, for example, of a minute ormore can be accommodated depending of course on the controls, the vaporbeing detected and the microorganism in use during the test. The shortpulse of test air or atmosphere does not appreciably change thebioluminescence of the detector.

Considering the portability of the embodiment of FIG. 1, it will beappreciated that a remote control unit can be stationed in the sensorassembly unit 14 for remote control operation at the hand-held unit.

An alternate preferred embodiment of the invention is illustrated inFIGS. 3 and 4. As hereinbefore stated, an embodiment according to theprinciples of the disclosure of FIGS. 1 and 2 has a sensor assembly unit14 which is operable while remotely disposed from a base assembly unit16. Where compactness is a desirability, an embodiment according to theprinciples of the disclosure of FIGS. 3 and 4 is more suitable. Here, asbefore, a sensor 50 is similarly disposed for receiving fluid cleansedby a filter 51 and moisturized by a humidifier 52 and circulated by apump 54 through a valve 56 defining either a recirculating path, whendisposed as illustrated in FIG. 3, or a sample test path, when disposedas illustrated in FIG. 4. Humidified and cleansed air passes from thehumidifier 52 through a conduit 58 to and through a closed recirculatingchannel 60 internal to the valve 56 to be carried through a conduit 62to directly communicate with the culture of the sensor assembly 50. Whenthe valve is disposed as illustrated in FIG. 3, the recirculating pathis continuous and is a substantially closed loop from sensor assembly 50through conduit 64, in communication with the pump 54, to and throughconduit 66 connected directly between the pump 54 and the humidifier 52.The conduit 64 constitutes the outlet port of the sensor assembly 50.During the recirculating mode the environment of the bioluminescentmicroorganism of sensor assembly 50 is conditioned and the culturemetabolism is stabilized by the passing of the humidified air across it.

In order to sample the atmosphere for a specific vapor, a control systemunit 67, provides for an actuator 68 to move the valve 56, asillustrated in FIG. 4, to define a fluid intake path. Fluid sample fortest is brought in through an input conduit 70 to pass through a closedchannel 72 internal to the valve 56 to pass through sensor input conduitor inlet port 74 to come in direct fluid contact with the predeterminedvapor sensitive culture in the sensor assembly 50. During the period ofsampling, the pump 54 operates to draw the sample across the culture ofthe sensor assembly 50, and through the pump 54 and the humidifier 52 tovent it to the outside atmosphere through output vent 75. After a samplehas been tested any remaining test gas is purged from the system duringthe recirculating mode of FIG. 3 by means of a bypass conduit 76 influid communication with the atmosphere through the closed internalchannel 72 communicating with the sample input conduit 70 through ashort channel 78 also internal to the valve 56.

The components for the two alternate embodiments, including the fluidconduit and the materials of all the elements disclosed herein aresubstantially similar. The sensor assemblies 10 and 50 are of likeconstruction and each generally defines an inner chamber disposed aboveor about a readily replaceable microorganism element. The microorganismelement is disposed within the inner chamber such that both therecirculating humidified fluid conditions the environment to precludeloss of moisture from the sensing element and the fluid samplesufficiently contacts or is exposed to the sensing element for thesensing elements to react with certainty when the specific vapor undertest is present in the sampled atmosphere. In addition, in order toidentify changes in the bioluminescent characteristics of the sensingelement when it reacts to the presence of a specific vapor, there areincluded photosensitive transducers which are not illustrated but, forexample, can be cadmium-sulfide photoresistive cells.

The humidifiers 12 and 52 are constructed such that they can bemaintained and include a moisture retaining medium such as sterilecotton or felt which can be saturated with water, preferably purified,and be maintained at a sufficient level to keep the chamber of thehumidifier near or at 100% humidity. The humidifier, in conjunction withthe respective filter or a suitable scrubber, will also cleanse the airby adsorption, absorption or by reacting with the organic elementscarried in the air sample. Activated charcoal comprises a suitablefilter element.

The pumps 18 and 54 are of sufficient size to circulate fluid throughthe system but generally require very little power and can, for example,be battery operated. A small diaphragm or rotary vane pump is suitablefor such embodiments. The valves 20 and 56 are illustrated as slidevalves, although it will be appreciated that other valves such as arotary valve are likewise suitable for operation in the illustratedembodiments. The actuators 22 and 68, as illustrated, are preferablyelectrical solenoids operable to move the valve to assume the samplingmode position as best seen in FIGS. 2 and 4. It will be appreciated thatother actuators could move the valve from its sampling mode position tothe recirculating mode position of FIGS. 1 and 3. Such actuators mightlikewise be electrical solenoids or mechanically biased springs and, inaddition, it will be appreciated that the valve position may be betterdefined if the valves latch or detent into position.

The control units 35 and 67, for example, might comprise normallyoperable switches, direct solenoid drives or latching solenoids, orlatching triggers with solenoid release and/or include timing elementssuch as electronic timers or dash pot timers for controlling theduration of the sampling period.

Successful operation of the system is dependent on having fluid tightintegrity within all of the illustrated components and in theconnections which extend between them. The fluid conduit is of anysuitable material which, like all the other components, is of suchphysio chemical makeup that it will not affect the responses expectedfrom the microorganism cultures. The material for the conduit, forexample, may be Teflon, stainless steel or high density polyethylene andthe conduit may be secured to the individual elements by stainless steelfittings. In the alternate embodiment of FIGS. 3 and 4, it will beappreciated that when the valve is in its recirculative position of FIG.3 the input conduit 74 is sealed and when the valve is in the samplingmode position of FIG. 4, the bypass conduit 76 is sealed. Likewise, whenbypass conduit 76 is sealed conduit 62, providing an input to sensorassembly 50, is likewise sealed.

It is claimed:
 1. A bioluminescent humidification method for testing forthe presence of a specific vapor in an air atmosphere, comprising thesteps of:recirculating humidified air during a non-testing period acrossthe surface of a bioluminescent sensor to control the humidity of thebioluminescent sensor; substantially interrupting the passing ofhumidified air across the bioluminescent sensor for a period of testing;passing during the period of testing air from the atmosphere to besampled across the bioluminescent sensor for testing for the presence ofa specific vapor in the air atmosphere; and then repeating the step ofrecirculating humidified air across the surface of the bioluminescentsensor to condition the bioluminescent sensor for detecting a specificvapor in the air atmosphere.
 2. Apparatus for testing for the presenceof a specific vapor in a fluid atmosphere being sampled, comprising:abioluminescent sensor assembly having a fluid inlet port for receivingsample fluid from a fluid atmosphere and a fluid outlet port and abioluminescent culture for responding to the specific vapor under testdisposed between and in fluid communication with the respective ports;humidification means in fluid communication with the sensor assembly forhumidifying fluid to pass across the bioluminescent culture tomoisturize the culture; a fluid communication system including fluidconduit and single valve means for cooperatively recirculatingmoisturized fluid between the humidification means and the sensorassembly, or for circulating sample fluid atmosphere through the inletport of the sensor assembly to the culture of the sensor and outward tothe fluid atmosphere through the outlet port of the sensor assembly tovent the sampled fluid when testing for the specific vapor; and pumpingmeans for cooperatively circulating fluid within the fluid communicationsystem to recirculate the humidifying fluid for moisturizing theculture, to sample the fluid atmosphere and to move the fluid intocontact with the culture to test for a specific vapor.
 3. The apparatusas defined in claim 2, wherein the valve means has a test sample inletin fluid communication with the atmosphere being sampled and a fluidoutlet in direct fluid communication with the inlet of the valve meansand the inlet port of the bioluminescent sensor assembly, the valvemeans additionally having a recirculative fluid path in directcommunication with the humidification means and the inlet port of thesensor assembly and said apparatus further including control means foractuating the valve means to provide fluid communication either betweenthe sensor and the humidification means through the recirculative fluidpath or between the sensor and the atmosphere being sampled through thetest sample inlet and the fluid outlet of the valve means.
 4. Theapparatus as defined in claim 2, wherein the inlet port of thebioluminescent sensor assembly is in direct fluid communication with thefluid atmosphere being sampled and the humidification means is in fluidcommunication with the inlet port of the sensor assembly and the valvemeans is connected between the outlet port of the sensor assembly andthe humidification means and provides fluid communication in either acontinuous loop fluid path between the inlet and the outlet ports of thesensor assembly and the humidification means to humidify thebioluminescent culture of the sensor assembly or vent the sensorassembly at the outlet port to the atmosphere when sampling fluidatmosphere through the inlet port of the sensor assembly.
 5. Theapparatus as defined in claim 4, wherein the valve means includes asliding valve having a first internal fluid path for venting the sensorassembly through the outlet port to the atmosphere when sampling thefluid atmosphere through the inlet port in the sensor assembly and asecond internal fluid path comprising a part of the continuous loopfluid path for humidification of the bioluminescent culture.